36
13.2 Grounding
A grounding lug is provided near the contactor for a ground wire.
13.3 Control Wiring
If the low voltage control wiring is run in conduit with the power supply, Class I insu-
lation is required. Class II insulation is required if run separate. Low voltage wiring
may be run through the insulated bushing provided in the 7/8 hole in the base
panel, up to and attached to the pigtails from the bottom of the control box. Conduit
can be run to the base panel if desired by removing the insulated bushing.
A thermostat and a 24 volt, 40 VA minimum transformer are required for the control
circuit of the condensing unit. The furnace or the air handler transformer may be
used if sufficient. See the wiring diagram for reference. Use Table 5 to size the 24
volt control wiring.
Verify the connectors on data lines 1 & 2 are plugged together. The connectors are
located on the inside of the control box in front of the ground lug.
14.0 START-UP – CHECKING AIRFLOW
The air distribution system has the greatest effect on airflow. The duct system is
totally controlled by the contractor. For this reason, the contractor should use only
industry-recognized procedures. The correct air quantity is critical to air conditioning
systems. Proper operation, efficiency, compressor life, and humidity control depend
on the correct balance between indoor load and outdoor unit capacity. Excessive
indoor airflow increases the possibility of high humidity problems. Low indoor airflow
reduces total capacity and causes coil icing. Serious harm can be done to the com-
pressor by low airflow, such as that caused by refrigerant flooding. Each ton of cool-
ing requires between 375 and 450 cubic feet of air per minute (CFM). See the man-
ufacturer’s spec sheet for rated airflow for the system being installed. Duct design
and construction should be carefully done. System performance can be lowered
dramatically through bad planning or workmanship. Air supply diffusers must be
selected and located carefully. They must be sized and positioned to deliver treated
air along the perimeter of the space. If they are too small for their intended airflow,
they become noisy. If they are not located properly, they cause drafts. Return air
grilles must be properly sized to carry air back to the blower. If they are too small,
they also cause noise. The installers should balance the air distribution system to
ensure proper quiet airflow to all rooms in the home. This ensures a comfortable liv-
ing space.
These simple mathematical formulas can be used to determine the CFM in a resi-
dential or light commercial system. Electric resistance heaters can use:
CFM =
volts x amps x 3.413
SHC x temp rise
!
WARNING
THE UNIT MUST BE PERMANENTLY GROUNDED. FAILURE TO DO SO
CAN CAUSE ELECTRICAL SHOCK RESULTING IN SEVERE PERSONAL
INJURY OR DEATH.
